The invention relates to a windshield wiper drive, in particular a motor vehicle rear window wiper drive, and to a motor vehicle with a windshield wiper drive.
In known rear window wiper drives, the transmission housing usually has an output dome which penetrates a rear window or the vehicle body, the output dome in turn being penetrated by the wiper shaft. In order to fasten the windshield wiper drive to the rear window or to the vehicle body, there is provided at an end of the output dome an external thread which serves to receive a nut by tightening which the transmission housing can be fastened to the rear window or to the vehicle body. The seal between the wiper shaft and the opening in the output dome is effected by means of an annular seal which is received in a region located radially between the wiper shaft and the internal circumference of the output dome. In order to protect the wiper shaft exit region additionally against direct exposure to water, it is known to fit a protective cap made of a thermoplastic material over the wiper shaft and the nut, the protective cap being fixed relative to the wiper shaft according to a first known variant, and the protective cap being arranged to rotate with the wiper shaft according to a second known variant. A disadvantage of both variants is that water, in particular saline and contaminated water, can penetrate the region enclosed by the protective cap through swirl and therefore, after spending a certain time on the annular seal, will necessarily advance into the interior of the housing. Especially in the case of a fixed protective cap, the latter is unavoidably subjected to wear at the interface with the wiper shaft, necessarily leading to additional leaks over the service life thereof. In the case of a protective cap which rotates with the shaft, the gap between the nut and the protective cap must the selected sufficiently large for the protective cap to be able to rotate relative to the nut without contact, swirled water then being able to penetrate the space enclosed by the protective cap even more easily. Although, in this case, the water can drain from the region within the protective cap comparatively easily, residual substances such a sand, dust, salt, etc., remain in a region below the protective cap after drying, as a result of which the gap becomes ever smaller over the service life, or in some cases is even completely closed. At that time at the latest, the water which has entered cannot drain, or drain completely, and can therefore advance to the annular sealing element between the wiper shaft and the internal circumference of the output dome, leading to premature wear of the sealing element, and consequently to penetration of water into the interior of the housing.